Problem: A jar contains $4$ red marbles, $6$ green marbles, and $8$ blue marbles. If a marble is randomly chosen, what is the probability that it is not red?
Answer: There are $4 + 6 + 8 = 18$ marbles in the jar. There are $4$ red marbles. That means $18 - 4 = 14$ are not red. The probability is $ \frac{14}{18} = \dfrac{7}{9}$.